1. Field of the Invention
This invention relates to disk drives and, more particularly, to high-density arrangements of disk drives in enclosures and the cooling of such arrangements.
2. Description of the Related Art
Electronic devices such as disk drives are designed to operate within certain temperature ranges. However, when operating, devices such as disk drives may generate heat. If enough heat is generated to cause one of the disk drives to operate outside of its operational temperature range, problems may occur. For example, in some cases, increased temperature may cause a device to malfunction or behave erroneously. Sometimes, increased heat may even damage the electronic devices.
Historically, individual disk drives have not been particularly troublesome heat generating components. Most disk drives were adequately cooled using passive cooling techniques and/or by relying on a system fan, and thus overheating problems rarely occurred. As disk drives have become faster, however, their heat generation has increased. For example, as access speeds have increased, the spindle motors have become faster and more powerful. As a result, the spindle motors have also begun generating more heat. Thus, the cooling of individual disk drives is becoming much more of a concern than it has been in the past.
Another related cooling concern arises when multiple disk drives are placed close together within an enclosure. With rising data storage needs and decreasing storage media costs, more storage media such as disk drives may be included in enclosures. For example, a group of disk drives may be set up as a RAID (Redundant Array of Inexpensive/Independent Disks) system. Alternately, a group of disks may be arranged in a JBOD (Just a Bunch Of Disks) configuration, which is any group of disks that are not set up in any specific RAID configuration. A common engineering goal is to achieve high-density packaging of disk drives in an enclosure so that the overall storage system takes up a minimal amount of space. However, this goal is often hindered by the need to cool the disk drives. In many cases, the probability of heat-related problems increases as disk drives are packaged more closely together. For example, a disk drive""s ability to transfer heat away from itself may be reduced as the airflow over that disk drive is reduced. When multiple disk drives are packaged closely together, the airflow over some of the disk drives may be blocked by the surrounding disk drives. Additionally, the combined heat generation from all of the disk drives may create a much hotter area than each disk drive would create individually. Thus, the disk drives in a high-density arrangement are likely to be in a hotter environment due to the heat generation of neighboring drives. Furthermore, the disk drives may not be able to transfer as much heat away because the neighboring drives may be blocking their airflow. As a result of these types of factors, disk drives in a high-density arrangement may be likely to develop heat-related problems.
The likelihood of heat-related problems may be exacerbated by the construction of the disk drives themselves. For example, some disk drives are designed so that the sides of the drive chassis extend to create a bathtub-like enclosure around the printed circuit board. An example of this is shown in FIG. 1. The drive chassis 11 encloses the head disk assembly, which includes the disk platter, spindle, spindle motor, actuators, etc (not shown). The connectors 14 are used to connect a disk drive to other devices and facilitate the transfer of data to and from the disk drive 10. The rails 15 may be used to mount the disk drive within an enclosure. The printed circuit board 13, also referred to as a logic board, contains most of the logic that controls operation of and communication with the disk drive 10. The sides 11a and 11b of the drive chassis may impede airflow over the logic board 13 and thus limit the logic board""s ability to transfer heat away from itself. If such a disk drive is used in a system where many disk drives are tightly packaged together, the airflow and ability to transfer heat may be additionally reduced over the printed circuit board due to the xe2x80x9cbath tubxe2x80x9d sides and the chances of heat-related problems may be increased.
In some existing systems designed to provide adequate cooling for high-density arrangements of drives, elaborate cooling systems have been used. For example, in one existing system, a refrigeration system is connected to a disk drive storage using a pair of thin metal plates that sandwich a disk drive. The plates conduct heat away from the disk drive and are cooled by the refrigeration system to improve their heat-removing capability. In other systems, fans and heat sinks are added to disk drives to improve their cooling. While these systems may adequately cool the disk drives, they add an undesirable degree of complexity and may undesirably increase the overall size of the storage system.
Various embodiments of methods and systems for cooling high-density arrangements of disk drives are disclosed. In one embodiment, a storage system may include several stacked layers of disk drives and one or more air movers. At least some of the air movers may be configured to cool the disk drives by creating an airflow. The disk drives may be configured to operate as a network or computer storage system. Instead of being arranged in a traditional, aligned arrangement, the disk drives may be arranged in an offset or staggered arrangement. Thus, at least one disk drive in a first layer may be offset from an overlapping disk drive in a second layer. This offset is in a direction parallel to the plane that includes the first layer. As a result of this offset, at least part of one of the disk drives in the arrangement is exposed to more of the airflow than it would be exposed to in an aligned arrangement.
In some embodiments, every disk drive in the first layer may be offset from a corresponding overlapping disk drive in the second layer. In one embodiment, the entire first layer may be offset from the entire second layer. In one embodiment, the offset used may be a lateral offset. In another embodiment, the offset may be a longitudinal offset. In still another embodiment, both a lateral and a longitudinal offset may be used. In addition to being offset, the disk drives in one embodiment may be inclined so that they are not parallel to the airflow.
In one embodiment, the offset may create an air gap between overlapping disk drives. This air gap may be configured to divert a portion of the airflow, and as a result, at least part of one of the disk drives may be exposed to more of the airflow than it would be exposed to in a traditional, aligned arrangement. The air gap may, in one embodiment, divert the airflow so that the logic board of a disk drive is exposed to more of the airflow than it otherwise would be. In one embodiment, the air gap may divert the airflow so that the surface area of the disk drive is exposed to more of the airflow than it would be in an aligned arrangement.
The amount of the offset may be greater than the width of one of the xe2x80x9cbath tubxe2x80x9d sides of one of the disk drives in some embodiments. This amount of offset may expose the logic board of a disk drive to more of the airflow than it would be exposed to in an aligned arrangement. In one embodiment, a continuous air channel may separate stacks of the disk drives. The offset arrangement may, in one embodiment, not greatly increase the space consumed by the disk drives. As a result, in one embodiment, the enclosure housing the offset arrangement of disk drives may be the same size as it would be if the disk drives had an aligned arrangement. Furthermore, in one embodiment, the offset arrangement may not substantially affect the accessibility of the drives for connection, repair, hot swapping, or replacement. Thus, the physical accessibility of the offset arrangement of disk drives may be substantially the same as it would be if the disk drives had an aligned arrangement.
In another embodiment, a storage system may include several stacked layers of disk drives and one or more air movers. The disk drives may be configured to operate as a computer or network storage system. Each layer may include one or more disk drives. At least one of the stacked layers may be inclined so that it is not parallel to the primary direction of the airflow created by the air movers. As a result of this inclination, at least part of one of the disk drives is exposed to more of the airflow than it would be in a traditional, non-inclined arrangement. Furthermore, in one embodiment, all of the stacked layers may be inclined so that none of the layers are parallel to the airflow. In some embodiments, some of the disk drives may also be offset from each other in addition to being inclined.
In one embodiment, the degree of inclination may be such that a logic board or a surface area of the one of the disk drives is exposed to more of the airflow than it would be exposed to in a non-inclined arrangement.
The inclined arrangement may not greatly increase the space consumed by the disk drives in some embodiments. Thus, in those embodiments, the size of the disk drive enclosure housing the inclined arrangement of disk drives may be the same as it would be if the disk drives had a traditional, aligned arrangement. Similarly, in some embodiments, the inclined arrangement may not have a substantial effect on the accessibility of the disk drives for connection, repair, hot swapping, or replacement. Thus, in those embodiments, the inclined arrangement may have substantially the same physical accessibility as would be had in an aligned arrangement.
In another embodiment, a method for packaging a plurality of disk drives within an enclosure for use as a computer or network storage system is disclosed. The method includes installing one or more air movers in the enclosure and mounting several layers of disk drives within the enclosure. The air movers are installed within the enclosure so that, when operating, a first portion of the air movers cools the disk drives by generating an airflow. The disk drives are mounted so that at least one disk drive in a first layer is offset from an overlapping disk drive in a second layer. As a result of this mounting technique, at least a part of one of the disk drives is exposed to more of the airflow than it would be if the disk drives had been mounted in an aligned arrangement.
In one embodiment, mounting the disk drives may involve mounting them so that at least one layer of disk drives is not parallel to a primary direction of the airflow. In some embodiments, mounting the disk drives may involve mounting them so that every disk drive in a first layer is offset from a corresponding, overlapping disk drive in a second layer. The offset may be a lateral offset, a longitudinal offset, or both.
In another embodiment, a method of cooling a plurality of disk drives within an enclosure is disclosed. The method includes performing memory transfers to or from the disk drives, one or more of the disk drives generating heat, and generating an airflow over offset or inclined regions of the disk drives within the enclosure in order to cool the disk drives. The disk drives are arranged so that one or more layers of the disk drives are offset from each other or so that one or more layers of the disk drives are inclined against the primary direction of the airflow. As a result of this arrangement, at least part of one of the disk drives is exposed to more of the airflow than it would be exposed to if the layers were arranged in a traditional, aligned, and/or non-inclined arrangement.
In another embodiment, a storage system may include several stacked layers of disk drives and one or more air movers. Each layer may include one or more disk drives. The disk drives may be configured to operate as a computer or network storage system. The disk drives and the air movers may be mounted within an enclosure. At least one of the stacked layers may be inclined so that it is not parallel to the floor of the enclosure. As a result of this inclination, at least part of one of the disk drives is exposed to more of the airflow than it would be in a traditional, non-inclined arrangement. Furthermore, in one embodiment, all of the stacked layers may be inclined so that none of the layers are parallel to the floor of the enclosure. In some embodiments, some of the disk drives may also be offset from each other in addition to being inclined.